The DE-A-38 17 695 (JP-P No. 62-129360) discloses a ceramic pressure sensor of the type defined and a method of manufacturing thereof. First, a green ceramic diaphragm is formed. Furthermore, a green ceramic base plate is formed. These two elements are then put together to a laminar body (by applying pressure) which is subsequently burned to form by connecting at the contiguous contact surfaces in a unitary burned ceramic sensor body.
With this sensor several method steps are necessary since the diaphragm and the base are formed separately, then combined to a green element and only burned thereafter. In particular with the manufacture of such a pressure sensor having a cavity provided adjacent to the diaphragm this manufacturing method is rather complex since there is inserted a further frame-like spacing element between the diaphragm and the base and the opening for the cavity in the spacing element and the passage in the base element must be filled with a sublimable disc insert and a rod insert, respectively, before putting these individual parts on each other to one unit and burning it together.
This combined burned sensor body is inserted into a housing and is clamped at the peripheral portion close to the diaphragm. This results in tensions in the diaphragm negatively affecting the measuring accuracy.
The U.S. Pat. No. 4,382,247 discloses a pressure sensor comprising a flexible diaphragm attached as a separate element to a plane rigid base plate. Depart from the vaguely defined shape of the diaphragm resulting in considerable inaccuracies of measurement manufacturing of the known sensor is complex.
The U.S. Pat. No. 4,481,497 discloses a pressure sensor employing a ceramic substrate and a ceramic diaphragm formed as separate parts and connected together. The substrate is provided with a cavity allowing deformation of the diaphragm. The diaphragm is provided with transducer means comprising a resistor bridge. Again, the known pressure sensor is complex in design and costly to be manufactured.
The DE-A-35 10 042 (U.S. Ser. No. 591,728) discloses a pressure sensor comprising a pressure transducer and a pressure measuring capsule. The capsule includes a membrane in surface contact with a diaphragm of the pressure transducer. The membrane of the capsule forms one wall of a cavity further defined by an opposite rigid plate and flexible transition portions connecting this plate with the membrane. Again, the design of the known pressure transducer is complex and the manufacturing thereof costly.
The U.S. patent application Ser. No. 322,142 relates to a pressure transducer comprising a rigid body formed of ceramic material with a ring-like shape having a central opening and a radially extending plane end surface, a diaphragm unitary with the rigid body and covering the opening at an end surface opposite to the plane end surface and thickfilm resistor means applied to at least one of two main surfaces of the diaphragm. Whilst this pressure transducer has a relatively simple design and is easy to be manufactured, it is difficult to position and fix it to a measuring position with the tendency of the diaphragm to be inadvertently tensioned or twisted.